1. Field of the Invention
The present invention generally relates to an optical recording medium. More particularly, the present invention relates to an organic compound for a recording layer for high speed recording and an optical recording medium including the same.
2. Description of Related Art
In recent years, development of optical recording media employing laser have been remarkable. An example of the optical recording medium, such as an optical disc, is generally designed to irradiate a focused laser beam of about 1 μm to a thin recording layer formed on a disc shaped substrate to conduct information recording. The recording is implemented in a manner that upon absorption of the laser beam energy, the irradiated portion of the recording layer undergoes a thermal deformation such as decomposition, evaporation or melting. Reading the difference in the reflectance between the portion having a deformation formed by the laser beam and the portion without such deformation carries out reproduction of the recorded information.
Accordingly, an optical recording medium is required to efficiently absorb the energy of the laser beam, and is also required to have a predetermined amount of absorbed light to a laser beam having a specific wavelength employed for recording and to be high in the reflectance to laser beam having a specific wavelength employed for reproduction for accurately conducting the reproduction of information.
However, storage capacity of the optical recording medium employing the laser source is limited due to optical diffraction. At present, some principles and methods of enhancement of the storage density of the optical information storage media are being set forth, including such as shifting of the wavelength of the laser source, for example, from red laser to blue laser, or enhancement of the objective numerical aperture (“NA”) of optical lens. Some other methods include improvement of the encoding methods of the digital signal, or a disc storage method using an extra-fine resolution near field optical structure, or a technology for increasing the storage capacity of the information storage media (e.g., a compact disc) by using stacked multiple recording layers, i.e., the recording layers of the information storage media is developed into a three dimensional space multilayer structure, to increase the storage capacity. All the methods described above may be employed to effectively increase the storage capacity of the optical recording medium.
In the method of the shifting to shorter wavelength laser source, a new generation of a high density disc storage specification (BLU-RAY DISC®) is published in 2002 by companies such as Hitachi, LG, National, Pioneer, Philips, Samsung, Sharp, Sony and Thomson Multimedia in common. A single-side BLU-RAY DISC® may be promoted up to 27 GB by employing a 405 nm blue laser source and a 0.1 mm optical transmission cover layer structure. Thus, optical recording medium employing a short wavelength laser source for reading and storage operations has become the main stream of the development.
In addition, high speed recording of information is limited due to requiring high writing power, which would generate excess heat. However, when recording is implemented at a high speed (a high linear velocity) by employing high writing power using a laser beam, heat distribution of the recording layer in an irradiated area is likely to become rapidly high resulting in a possibility that the cross-talk phenomenon becomes more pronounced or worse adversely affecting the quality of the signal.